Telephone system



i4, g. C, GILUNGS E1- AL L9U'5 TELEPHONE SYSTEM Filed June 1, 1951 9 sheetissheet 1 "alch 4, H933. C. GILUNGS ETAL LQ TELEPHONE SYSTEM Filed June l, 1951 v 9 Sheets-Sheet 2 March M, 1933- c. GILLINGS ET AL LQMM TELEPHONE SYSTEM Filed Jun 1, 19:51 9 sheets-sheet 5 52M SRM SVM Imm-5F? Charlas Erlln s Francis T'lcxck Balas.

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Marek M, 1933 c. GILLINGS ET AL 11,901,156

TELEPHONE SYSTEM Filed June l, 1951 9 Sheets-Sheet 4 FIGZ. Ha.

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Charles 1 ugs Frm-1cm 'Ta-Hack Balas www AMrlh 14, /1933- c. GILLINGS Er Al. 1,901,156

TELEPHONE SYSTEM Filed June 1, 1931 9 Sheets-Sheet 5 Franci: TEU.: ckn'llm March 14, 1933. GlLLlNGs ET AL 1,901,156

TELEPHONE SYSTEM Filed June l, 1931 9 Sheets-Shea?I 6 March 14, 1933.

C. GILLINGS ET AL TELEPHONE SYSTEM Filed June 1, 1951 9 Sheets-Sheet 7 Charles Billings .Fx-:anais muck Ella' March 14, 1933. c. GILLINGS ET AL TELEPHONE SYSTEM 9 Sheets-#Sheet 8 Filed June l, 1931 Bibs Char-1an Eil Fmi www Francis Ta1'1Dck March 14, 1933- c. GILLINs ETAL I 1,901,156

TELEPHONE SYSTEM Filed June l, 1931 9 Sheets-Sheet 9 @.9 SAR aR H p 5br4 Q IH; san Scr di I1-Lul. nrs- Charlas Billing: Francis 'T''luck Bilal i Patented Mar. 144, 1933 UNITED sTATEs PATENT OFFICE i CHARLES GILLINGS ANI) FRANCIS TATLOGK BELAS, OF LIVERPOOL, ENGLAND, A S- SIGNORS TO ASSOCIATED TELEPHONE AND TELEGRAIH COMPANY, 0F CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE TELEPHONE SYSTEM Application iiled June l, i931, Serial No. 541,286, and in Great Britain Iune 23. 1930.

The present invention relates to telephone systems and is more particularly concerned with systems em loying register controllers of the code trans ating type. In a system of this type in use the cal ing subscriber dials three exchange digits and then four numerical digits. These are stored by the register controller which then transmits up to six routing digits having an arbitrary relationship to the exchange digits, and subsequently transmits the four numerical digits unchanged.

It is found that the last choice junctions between exchanges are employed in a very inefiicient manner as they carry only a small percenta e of the total trac and it is an object o the present invention to effect an economy in the number of junctions required by providing direct junctions for about 90% of the total tralic and by routing the resulting overflow trailc through a tandem channel. This results in a considerable reduction in the number of direct junctions and only a slight increase in the number of tandem junctions. In the case of a large area employing a main tandem exchange and a number of sub-tandem exchanges, it is possible by means of the invention to arrange for a register controller to re-route calls either by way of the main tandem exchange or by way of any one of the subtandem exchanges. l

According to one feature of the invention in a telephone system employing register controllers, in the event of an all-trunksbusy condition being encountered durin the setting up of a connection a signal is sent ack over the trunk conductors to cause the l register controller to effect the release of the partially set up connection and the transmission of trains of' impulses fof different value to set up the call over another route.

According to another feature of the invention a register controllerfis arranged so that the transmission of successive trains of impulses for setting automatic switches is effected under the control of a step-by-step switch adapted in its initial positions to control the transmission of'impulses correi sponding to a wanted exchange Aby connecting up in turn certain of the wipers of a switch which is set in response to incoming impulses characteristic of that exchange, the control switch being adapted in later positions to control the transmission of one or more trains of impulses which are the same foraplurality of exchanges and in still later positions to connect up further wipers of the impulse res onding switch to control the transmission o further trains of impulses corresponding to the wanted exchange.

The invention will be better understood from the following description of several methods of carrying it into edect which should be taken in conjunction with the accoigpianying drawings comprising Figs. 1

It is proposed to describe three arrangements for re-routing calls via a single tandem exchange and one arrangement for rerouting calls via one of a number of tandem exchanges. For the benefit of greater clearness, the arrangement illustrated in Figs. 1 6 shows full circuits of the first code selector. A digit switch finder, A digit switch and register controller and the portions of the apparatus which are known have been briefiy described. As regards the two alternative methods shown in Figs. 7 and 8 of -re-r uting a call via a single tandem exchange and the method shown in Fig. 9 of rerouting a call via any one of a number of tandem exchanges, however, it has been thought suilicient to show only the portions of the equipment which differV from the arrangement shown in Figs. 1 6.

Referring now to Figs. 1-6, illustrating the first embodiment of the invention, which should be arranged as shown in the right hand bottom corner of Fig. 3 to form a complete circuit, Figs. l and 2 show a first code selector coupled to an A digit switch finder AF. Fig. 3 shows a second code selector which like the first code selector is arranged for simultaneous hunting by means of both its sets of wipers. Fig. 4 shows an A digit switch .and Figs. 5 and 6 together illustrate a register controller.

Assuming that a calling subscriber has been connected to the first code selector shown by way of a non-numerical switch such as a rotary line switchor the like, relay L will operate over conductors 10 and Il in series with the calling subscribers line and instrument, and at armature Z1 operates relay A in series with relay I and the.righthand winding of relay D, and at a-rmature Z2 operates relay B. Thereupon at armature b2 the release trunk conductor 12 is earthed, and at armatures b3 and a3 a circuit for relay C is completed. When relay C operates the A digit switch finder AF will commence hunting for a free A digit switch, the circuit for the step-off from the home position being from earth in the routiner access equipment (indicated by a dotted connection), bank contact and wiper 3a of the A digit switch finder AF, armature b4, lower winding of relay K (in arallel with earth, armature m2, resting contacts of off-normal springs N2', armature a1, upper winding of relay K),

.armatures k1 and c2, magnet interrupter springs afdm, armature ml, ri ht-hand winding of relay MG to battery. elay K does not operate in this circuit owing to the high resistance of relay MG, but the latter relay operates and at armature mgl completes a circuit for the A digit switch finder driving magnet AFDM, which therefore oper,

ates and at interruptersprings afdm breaks the circuit of relay MG which thereuponreleases and breaks the magnet circuit again. The driving magnet therefore restores and advances the wipers of the switch AF to the next set of contacts which extend to an A digit switch. If this is free, the contact which wiper 3a engages will be marked by low resistance battery by way of the left-hand winding of relay IB of the A digit switch, Fig. 4, in arallel with resistance IYB so that relay will be enabled to operate to earth at armature m2. Relay MG is now unable to operate as under these conditions its high resistance right-hand winding is shunted by the low resistance battery connection. Relay K upon operating, at armature I, locks up and short-circuits its upper hi h resistance winding thereby permitting t e operation of rela IB in the A digit switch. At armatures 5 and k6, relay A is switched over to hold in series with resistance IYA in the A digit switch and at armature 102 a circuit is completed for relay IA in the A digit switch in series with the lower winding of relay B which is maintained operated in this circuit. It should be pointed out that had the A digit switch been already in use by another first code selector, earth through the low resistance holding winding of relay K of this latter switch would have prevented the operation of relay K in the first code selector under consideration and would have enabled relay MG to o erate, thus allowing the driving magnet A DM to step the wipers to the next set of contacts in search of an idle A digit switch. When relay IA operates, armature Ial completes Aa circuit for operating relay IC over its left-hand winding, thereupon by the operation of armature 104 dial tone from the transformer DTT is transmitted by way of condenser IGA to the calling subscriber to inform him that he ma now dial the number of the wanted subscri r.

Upon the reception of the first train of impulses, relay 1 in the first code selector will de-energize intermittently at armature l2 will repeat the impulses to relay IA which will in consequence at each restoration complete a circuit for the operation of the vertical magnet IVM of the A digit switch. The shaft and wipers of this switch are therefore raised to the required level, and relay -IC being slow remains operated over its .low resistance right-hand Winding in series with the vertical magnet IVM during` the impulse train. A digit switch is arranged to release automatically in case only a single impulse is sent to it, as might be done in error due to the subsprings IN3, armatures Igl and HI to earth.

The A digit switch will thereupon be restored to normal in readiness for the rece tion of the setting impulses. from the su scribers dial.

On the de-energization of relay 1C, a circuit is completed for the rotary magnet IRM over armature 102, whereupon the wipers Ib to 5b are rotated into engagement with the first set of contacts in the level chosen which extend to a register controller such as that shown in Figs. 5 and 6. If this is already in use, the contact upon which wiper 3b is resting will be marked by earth by Way of the low resistance winding of relay H in this latter switch and the low resistance winding of relay K in the associated first code selector in series. When, therefore, the rotary magnet interru ter springs IR operate near the completion o the rotary step, the right-hand winding of relay IG will be energized from this earth in series with the low resistance upper winding of relay H which however will not operate in this circuit. Relay 1G, however, operates and breaks the circuit of the rotary magnet at armature Zgl, whereupon the rotary magnet vde-energizes and opens the circuit of rela tti IRM and relay 1G continues until a disenga ed register controller is found, which will e assumed to be the one shown 1n Figs. 5 and 6. Relay H then operates in series with resistance 2YA, Fig. 45 of the register controller and at armature b1 opens the circuit of the rotary magnet lRM and at armatures h2 to h5 connects up the various control leads to wi rs 1b to 5b of the A digit switch.

elay 2A of the register controller now operates over ulse conductor 2C in series with relay B of the first code selector and at armature 2a1 energizes relay 2B. This relay thereupon at armature 2114 prepares the impulsing circuit, at armature 253 removes the shortcircuit across the winding of relay BA, thereby permitting this relay to operate and at armature 252 connects earth to the hold lead 37. Relay BA upon operating locks up at armature ba=2 and at armature ba5 a plies earth to the impulse machine start con uctor 34 in order to start the motor driving the ulse springs OPS which transmit pulses or settin the selectors and also the pulse springs Si; S which serve to step the sender switch SS.

Upon the reception of the second code digit, which is the first digit to take effect in the register controller, relay 2A will restore each time relay L of the first code selector restores and at armature 2a1 will transmit a corresponding number of impulses to the yertical magnet 2VM of the so-called 13C switch thus stepping the wipers ofthis switch to the level corresponding to the digit dialled. Relay 2C is operated in series with the magnet on the first impulse and remains operated during the train of impulses due to the slug fitted on its core. At armature 202 the driving magnet UDM of the switch US is energized over its own bank Contact and wiper 3c to earth by way of armature 2b2 and sprinfr BKl of the busy key so that when relay 2O restores at the end of the impulse train, the wipers of switch US are advanced to the next set of contacts. rlFhe next impulse train will therefore operate the rotary magnet 2RM of the BO switch thus rotating the wipers 1d to 6d of this switch into enga ement with the set of contacts associated wit the exchange name dialled. At the conclusion of the impulse train, the units digit switch will again be advanced one step so that the first or thousands numerical digit of the number dialled will operate magnet ThDM to set the wi ers of the thousands numerical digit switch HS. In a similar manner the remaining numerical digits transmitted to the register controller will serve to operate the hundreds, tens and units switches respectively. It may be pointed out that the units switches serve also as a digit distributor and accordingly the wiring of its sender control bank musttake account of the fact that it is standing in position 6 when the units digit is sent to it instead of position 1 as the case with the other numerical digit register switches.

As soon, however, as the wipers of the units digit register switch have reachedv the third set ofA bank contacts, that is to say, after the final two exchange code digits have been stored, the register controller will commence to send out impulses to set up the necessary train of switches to route the call to the wanted exchange. It will be seen that upon the next occasion when the impulse springs SPS break after switch US has advanced to third position, relay 1G will operate from earth over wiper busy key springs BKl, armature 2b2, lead 37, wiper 2c and its third bank contact, first bank contact and wiper 3e, lead 39, armatures brl, ldl, .921, and co2 and at armature Zg2 will connect the sender switch driving magnet SDM to the same earth by way o the pulse springs SPS so that when the latter close agaln the magnet SDM is ener ized and steps the wipers of the switch S when its circuit is broken upon the next opening of the pulse springs SPS, so that by this means the wipers of the sender switch SS will .be rotated under control of the pulse springs SPS. When the sender switch SS reaches lts third position the pulse springs OPS which have hitherto been short-circuited by the wiper 2f and bank wiring of the sender switch SS are connected by the saine agency across the conductors 18 and 19 which are now connected to relay A in the first code selector. The spring combinations OPS and SPS are arranged to operate at the same speed but in opposition so that when springs OPS are opened springs SPS are closed and vice versa. Therefore after each step of the switch SS the circuit of relay A of the first code selector will be opened and it will deenergize and at armature a3 complete a circuit for the vertical magnet VM in this switch.

It should be explained at this point that the banks of wipers 1d to 6d of the BC switch are cross-connected by means of a suitable distributing frame to bank contacts of wiper 4f, this cross-connection serving to determine the translation of the exchange code digits into the trains of impulses necessary to route the call to the particular wanted exchange.

Assuming, for example, that the exchange code digits dialled by the subscriber are 325, then the digits to take effect in the register controller will be 25, the first or A digit., namely 3, having been absorbed .by the A digit switch, so that the wipers of the BO switch will be stepped to the 5th contact in the 2nd level. Suppose further that it is necessary for the register controller to transmit the digits 753 for the correct routing of the call to the required exchange, then the BC switch bank contact upon which wiper 1d is resting will be cross-connected to the tenth contact in the bank of wiper 4f and since the register controller will only commence to send out pulses when the wipers of switch SS reach their'third set of contacts it is evident that seven pulses will have been sent out over conductors 18 and 19 before wiper 4f reaches the contact under consideration. When this occurs relay SZ will operate in the following circuit: earth, busy key springs BKl, armature 262, lead 37, wiper 2c and bank contact of switch US, lead 38, wiper 2e and first bank contact of switch CS, Wiper 1d and bank contact of BC switch, jumper connection, bank contact and wiper 4f of switch SS, winding of relay SZ to battery. Relay SZ thereupon at armature S24 short-circuits the impulse springs OPS in order to stop the sending out of impulses.

The effect on the first code selector will be to cause it to step its wipers to the seventh level and when relay C falls away at the completion of the impulse train the rotary magnet RM of the first code selector will be operated over armature c1 and will rotate the wipers into engagement with the first sets of contacts on the seventh level. If the switches associated with both these sets are already in use, the contacts with which wipers 5g and 6g engage, hereinafter referred to as the P1 and P2 bank contacts respectively, will both be marked by earth so that relay G will operate over its left-hand winding when the rotary magnet springs R close at the end of the rotary step and at armature g4 will break the circuit of the rotary magnet RM thus allowing` the latter to release and break the circuit of relay G at the interrupter springs R. The right-hand holding winding of relay G is ineffective at this time, since it is being short-circuited by the earth on the P2 bank contact over wiper 6g on one side and on the other by the operating earth for the rotary magnet RM. Relay G will therefore restore and again complete the circuit of the rotary magnet RM at armature g4, and in this manner the rotary hunting motion in search of a free second code selector will take place. If a pair of contacts are encountered in which the P1 bank contact is free, relay HA will operate in series with the left-hand winding of relay G, the latter relay being unable to operate in this circuit. The second code selector associated with the contacts upon which wipers 1g, 2g and 5g are resting will thereupon be taken into use and on the operation of armatures ha?, and M4 relay 3A in this latter selector will operate over the loop completed across conductors 18 and 19 in the register controller. The operation of relay HA as above described is independent of the conditions of the P2 contact. If the P1 contact is busy, however, while the P2 contact is idle, relay HA will be unable to operate and relay HB will operate in series weidse magnet SDM by way of interru ter springs sdm. After a few steps of the riving magnet, however, another circuit is completed for relay IG over armature 322 and a group of commoned bank contacts of wiper 1f to earth. The switch will only stop over these contacts under control of the pulse springs SPS so that a definite interval equal to several impulses must elapse between any two consecutive trains of impulses sent out by the register controller. This feature is provided to cover adequately the hunting times of the various switches which are being set by the re ister controller in the routing of the call.. hen the switch SS has completed its last few steps by self-interruption, relay SZ will restore'and at armature sel again complete the original operating circuit for relay 'IAG after which the second routing digit will be sent out in a manner similar to that described above. It will be seen that the operation of armature 823 on the completion of sending the first routing digit will also break the circuit of the magnet CDM which will therefore step its wipers on to the next set.

of bank contacts so 'that the bank contact upon which wiper 2d of the BC switch is now resting will be marked by earth over wiper 20 and bank contact of switch CS. In the example under consideration it will be remembered that the second digit to be sent out from the register controller to route the call correctly is 5 so that the bank contact upon which wiper 2d of the BC switch is now resting will be cross-connected to the 8th contact in the bank of wiper 4f of switch SS. Five impulses will therefore be transmitted over conductors 18 and 19 to the second code selector before rela SZ is operated over wiper 4f of the switc SS, so that the vertical magnet 2VM of the second code selector, Fig. 3, steps the wipers of this switchto the fth level after which the relay 3C will restore and complete the circuit of the rotary magnet SRM at armature 301. Hunting for a disengaged succeeding selector will thereupon take place in a manner similar to that already described for the case of the first code selector, and, when an idle selector is found, either relay lHA or relay lHB will switch through the conductors after which the selector taken into use will be operated by the third train of impulses sent out by the register controller.

It should be pointed out that if less than three digits are required to route the callto Aas los

the required exchange, for example, if only two digits are required, then the contact upon which the wiper 3d of the BC switch is restin will be cross-connected to the digit cutolfg terminal DGO to which the magnet CDM is connected over its interrupter springs calm, so that when this contact becomes marked by earth owing to the stepping of the wiper 2e of the control switch a circuit will be completed for the control switch driving magnet CDM by way of interrupter springs edm and therefore its wipers, including wiper 2e, will be advanced to the next set of contacts.

If it is assumed that the call is successfully routed to the required exchange by a maximum of three routing digits, it will `be seen that since the terminal 9 is cross-connected to terminal DCO, the control switch will rotate its wipers until wiper 2e reaches the bank contact leading to wiper 2k of the thousands digit storing switch THS. The banks of the numerical digits storing switches with which wipers 2k, 3h, 3j and 5c engage are multiplied directly to the bank of the sender switch SS with which wiper 4f engages since no translation is necessary in the case of the numerical d' its.

The register controller will not commence to send out the thousands digit until the hundreds digit storing switch HUS has been moved oi normal in response to the hundreds digit, thereby rotating its wiper 2h on to the commoned bank contacts connected to the tenth bank contact and wiper 3e of the con trol switch CS and thence as previously traced to relay IG. By this means it is ensured that the storin of the thousands digit must be completed efore sending of this digit is commenced. Similarly the hundreds digit is not sent out until the tens digit storing switch has moved ofi-normal in response to the tens di `t. Sending of both the tens and the units igit may commence as soon as the units digit storing switch has commenced to respond to the units digit. After the units digit has been sent, the wiper 2e of the control switch CS will engage with the fourteenth bank contact which is connected to the cut-off terminal CO and over armature 825, right-hand winding ofrelay U0 to battery so that the cut-off relay CO will operate and thereupon lock up over armature co4 to the earth on lead 37. At armature co1 battery by way of relay BA and resistance 2YA is disconnected from conductor 22, thus allowing relay H in the A digit switch and relay K in the first code selector to restore as well as relay BA. The release of relay Hin addition to completing the circuit of the release magnet 1ZM of the A digit switch whereupon the switch is restored to normal also opens the circuit of relay 2A in the register controller. This relay accordingly deenergizes and brings down relay 2B whereupon the holding earth on lead 37 is removed, thus releasing relay CO and homing circuits are completed for the various switches 1n turn. The homing circuit for each successive switch, it will be noted, is completed over the homing bank and wiper in normal position of the preceding switch. The A digit switch and register controller will therefore restore to normal and the A di it switch finder AF will also return to the ome position, the homing circuit for the driving magnet AFDM being completed b armature k3.

Assuming the wanted su scriber to be free, he will now be signalled by ringing current transmitted from the final selector in the switch train and, when he answers, current will be reversed over the speakin conductors so that the polarized relay D in t e first code selector will operate and at armature d1 connect the right-hand windin of relay DA to springs controlled by the S pulse cam SP. The latter operates at regular intervals and upon its next operation will applbattery to the right-hand winding of relay A so that the latter operates and at armature da2 connects the lower winding of relay DB to springs controlled by the Z pulse cam ZP which is arranged to operate a predetermined period after the operation of the S pulse cam. Hence upon the operation of the cam ZP relay DB will operate and at armature dal and c1364 battery by way of resistance YA will` be connected to the meter conductor 43 to operate the subscribers meter, not shown, in order to register the call.

It should be mentioned that the first code selector A digit switch and register controller are fitted with arrangements for forced release in the case of omission or delay to dial on the part of the calling subscriber. For example, if the subscriber does not commence to dial within a predetermined period after the A digit switch has been taken into use, relay TP of the A digit switch will operate over its right-hand winding from earth supplied by the S pulse cam 1SP. Thereupon at armature tp4 the left-hand winding of relay IG is connected to the Z pulse cam lZP so that relay IG will operate when the latter cam becomes effective a predetermined time after the S pulse cam has operated. At armatures lgl and tp2 earth from armature h1 is connected to the forced release conductor 17, whence it is extended over bank contact and wiper 5a of the A digit switch finder AF, armatures m2 and 164, upper winding of relay M to battery so that relay M operates and locks to earth over armatures m3 and b2. At armature m6 the holding winding of relay K is short-circuited so that the latter relay restores and at armatures k2 breaks the circuit of relay A of the A digit switch thus allowing the A digit switch to restore. At armature m5 number unobtainable tone is transmitted to the calling subscriber by way of tone condenser QC, at armature m2 earth is applied to the supervisory conductor 33 resultln in the operation of a supervisory relay w ich lights the main supervisory lamp, and at amature m4 the lamp LP which is individual to the first code selector is connected to interrupted earth in order to attract the attention of the exchange attendant.

Similarly if, after the register controller has been taken into use, the calling subscriber allows too long a time to ela se between dialling any two digits, relay 1 P and then relay IM will be operated from the cams 2SP and 2ZP. Thereupon at armature 1m3 the sender switch SS is set in operation and when it has taken twelve ste s relay SZ is operated over armature 1m5. ence at armatures 1m4 and 896 earth will be applied to the forced release conductor 21 and so over the A digit switch to relay M in the first code selector, whereupon the force release of the A digit switch and the register controller will take place in a manner similar to that just described.

A detailed description will now be given of the re-routing operation of the register controller. Assume that in response to the first digit sent out from the register controller the first code selector steps its wipers 1g to 6g to a level in respect of which rerouting facilities are operative. Upon the wipers reaching this level the normal post springs NP will operate and since if all the outlets on this level are engaged the wipers will be driven to the eleventh rotary sition to operate the eleventh step cam sprlngs, a circuit for relay AR will be completed from earth, operated of-normal springs N5, lefthand winding of relay AR, operated cam springs S3, operated normal post springs NP, resitance YC to battery. Upon the operation of relay AR, at armature arl, the circuit for the switching relays HA and HB is broken and at armature ar3 a circuit is completed for the release magnet ZM of the first code selector from earth, armature m2, operated off-normal springs N2, armatures hb2, za2 and W3, winding of the release magnet ZM to battery so that the wipers of the first code selector are restored to normal. Moreover, at armature a1'2 earth by way of the left-hand winding of relay AR is connected over wiper 5a and bank contact of the A digit finder switch AF, conductor 17, armature h4, wiper 5b and bank contact of the A digit switch, conductor 21, and armature 1m4, to the left-hand winding of relay BR. Relay BR upon operating at this time at armature hr3 connects its right-hand winding in series with the driving magnet CDM of the control switch CS and owing to the low resist-ance of this winding magnet CDM is enabled to operate and drive the wipers of the switch CS to the fourth set of bank contacts. Relay BR also at armature brl disconnects wiper 3a of the control switch CS so as to prevent further sending taking place aslo`ng as relay BR is operated, and also at armature M4 completes a circuit for relay CR which operates and locks up at armature er1 to earth on lead 37. Relay CR also connects up the terminals corresponding to the code necessary for routing the call to the tandem exchange at armatures m2 -to W4 and at armatures m15 to 01'7 connects up wipers 4d to 6d to enable them to controi the routing from the tandem exchange to the desired exchange. As has already been explained, the first set of three contacts in the bank of wiper 2e of the'control switch CS has access over the wipers 1d, 2d and 3d of the BC switch to terminals corresponding to the code for routing the call direct 'to the required exchange, the second set of three contacts is connected over front contacts of relay CR to terminals corresponding to the code required for routing a. call to the tandem exchange, either as a normal procedure or as a result of the direct route being inaccessible, and the third set of three contacts has access over front contacts of relav CR and the wipers 4d, 5d and 6d of the BC switch to terminals corresponding to the code required for routing a call from the tandem exchange to the wanted eX- change. The next four contacts control the transmission of the numerical digits in the usual manner.

In the case now under consideration which involves rerouting of a direct call, it will have been seen that the routing digits are transmitted in the first three positions of the wiper 2e and if less than three routing digits are required the terminals selected over the wipers 2d lor 3d which are not required are cross-connected tov the digit cut-off terminal DCO.v If in response to the routing digits the connection is extended to the wanted exchange. the register controller continues to transmit uninterruptedly and the' control switch skips over its positions 4, 5, 6, 7, 8 and 9 since the corresponding contacts in the bank of wiper 2e are connected in this condition over resting armatures of relay CR to the terminal DCO and the numerical digits are then transmitted in the usual manner.

If however the connection to the wanted exchange is not completed owing to the first code selector failing to find an idle trunk, the operation of the register controller is stopped in the manner previously described. The circuit forl the left-hand winding of relay BR is opened when the first code selector has restored to normal and the circuit for the right-hand winding` when the control switch hasreached its fourth position. Relay CR is operated and connects the second set of three contacts in the bank of wiper 2e to terminals corresponding to the code for routing to the tandem exchange so that on the de-energiz'ation of relay DR the re ister controller will again commence -to sen and will transmit routing digits for setting up a connection to the tandem exchange. In po sitions 7 8 and 9 wiper 2e encounters contacts which have been connected by the 0 eration of relay CR to terminals correspon ing to the code for controlling the swltches in the tandem exchange to extend the connection to the Wanted exchange and these digits areaccordingly transmitted and are followed by the numerical digits in the usual manner. v

If the wanted exchange is one which is normally reached through the tandem exchange, the corresponding contacts engaged by wiper 1d and 2d are connected to the terminal DCU while the contact engaged by wiper 3d is connected to the terminal TC. The wiper 2e will accordingly skip over positions l and 2 and in position 3 will complete a circuit for operating relay CR which locks up and transfers contacts 4, 5, 6, 7, 8 and 9 from the terminal DCO to the terminals necessary for routing the call to the tandem exchange and from thence to the Wanted exchange. The numerical digits are subsequently transmitted in the usual manner.

If however, the first code selector finds an idle trunk to a second code selector, the register controller continues to transmit in normal manner and in response to the second routing digit the second code selectorsteps up to the corresponding level. If this level is associated with the re-routing facilities, normal post springs 2NP close, and connect booster battery to the eleventh stop dam springs 2S5, sothat if all the contacts in the selected level are busy, booster batteryv will be fed back over the test conductor to cause the operation of relay AR. Relay AR is adjusted so as not to operate when its righthand Winding is connected in series with battery fed through the windings of switching relays of subsequent switches in the train, but to operate when booster battery is fed back over the test conductor. Relay AR upon operating effects the circuit changes previously described.

Referring now to the arrangement shown diagrammatically in Fig. 7, this is very similar to the arrangement just described but is adapted for use where a separate forced release lead is not employed. In this case relay lAR of the first code selector is adapted to be operated either over its upper winding from earth, upper winding of relay IAR, armature 111.2, wiper fop and bank contact of the first code selector FCS, operated armature 661 in the second code selector, operated contacts of eleventh step cam springs 4S, operated contacts of normal post springs 4NI, resistance YA to booster battery BB, or over its lower winding from battery, low resistance lOwer winding of relay lAR, op-

erated contacts of eleventh step cam springs 3S of the first code selector, operated contacts of normal post springs 3N?, resistance 4YA to earth. Relay AR on operating, at armature larl completes a circuit for relay lBR of the register controller from earth, upper winding of relay lBR, armature 563, bank contact and wi er adp andarmature 2k6 of the A digit switch ADS, bank contact and wiper afp of the A digit switch finder ADF, operated off-normal contacts 4N of the'first code selector, armature larl, lower winding of relay IAR to battery. Relay BR is marginally Vadjusted and is not operated -by the normal current flow through relays 1K and 2H. When the low resistance winding of relay AR is connected up, however,

relay BR energizes and eects the circuit changes previously described.

Referring now to Fig. 8, this illustrates an alternative arrangement in which the signal which is sent back to the register controller to cause it to stop sending and subsequently to send a different code is transmitted over the impulsing circuit and the arranging is therefore independent of whether a separate forced release lead is employed or not. In the arrangement shown which in a preferred form the actual signal sent back over the impulsing circuit consists of a low frequency alternating current which causes the polarized relay 2D in the register controller to ener ize and deenergize successively. On the rst energization of relay 2D, a circuit is completed over armature Qdl forrelay QAR, which upon operating, at armature 2a1'1 closes a point in the circuit of relay 2BR. When relay 2D de-energizes relay 2BR operates in series with relay QAR, and at armature 261'3 opens the originalenergizing circuit' of relay 2AR and closes a point in the circuit of relay QCR. When relay 2D energizes for the second time, relay QCR operates and locks vup at armature 201'1. Relay 2CR also opens the circuit over the right-hand winding of relay 2BR and connects the comparatively low resistance lefthand winding in series with the release magnet of the first code selector. The release magnet therefore operates and restores the first code selector to normal after which relay 2BR releases and the register controller recommences to send and transmits the routing digits necessary for routing the call to the tandem exchange and from thence to the wanted exchange in the manner previously described.

Referring now to Fig. 9, this illustrates an arrangement for use in circumstances slightly different from those previously assumed. It will be assumed that it is convenient to divide a large system into an inner area and an outer area, and to provide a main tandem exchange in the inner area and a number of sub-tandem exchanges, for instance, four in the outer area. The main tandem exchange will then have junctions to all exchanges in both the inner and outer areas. The subtandem exchanges will have junctions to all 5 exchanges in the inner area only and each sub-tandem exchange will also serve a group of adjacent exchanges in the outer area, so that all exchanges-in the outer area have junctions to the main tandem exchange and one or other ofthe sub-tandem exchanges.

Calls from exchanges in the inner area may be routed via the main tandem exchange in a case where the wanted exchange is comparatively distant or via one of the subtandem exchanges in a case where the wanted exchange is located near to that sub-tandem exchange. Calls from exchanges in the outer area may be routed via the main tandem exchange in a case where the wanted exchange is comparatively distant or via the nearest sub-tandem exchange in a case where the wanted exchange is located near to that subtandem exchange.

If one of the routing switches fails to find an idle outlet, an overflow busy signal is trans'- mitted back to hold up the sending operation of the register controller and to cause the routing switches to restore to normal in any one of the three methods already described. The arrangement illustrated in Fig. 9 which shows only a portion of the register controller assumes that the method used is that illustrated in Fig. 8 whereby low frequency alternating current is transmitted back to the register controller over the speaking leads. Relay SCR is operated in these circumstances and is also operated over wiper 3p which is connected to terminal STC when the call is to be routed via the tandem exchange normally.

The necessary alteration in the translation for routing the call to any one of the subtandem exchanges is effected under the control of relays STA, STB and STC. These relays are connected in various combinations to terminals ST1, ST2, ST3, and ST4. When a call is normally routed direct but is capable of being re-routed via a sub-tandem exchange, the corresponding bank contact engaged by wiper 1p is connected to the appropriate one of the terminals ST1 to ST4 so that one or more of these relays will be operated; by its operation the relay will transfer the connection from wiper 1p to terminal 3DG() whereupon the control switch will connect up wiper 2p. Two code digits for direct routing will then be transmitted and these will be followed by the numerical digits if an idle junction to the wanted exchange is found.

If however no idle junction is available, sending will be stopped, the routing switches will be released and relay 3CR will be operated. By the operation of relay 3CR the connections from terminals 4, 5 and 6 engaged by wiper 2cm are transferred from terminal BDOO to terminals connected up under the control of relays' STA, STB and STC to provide the necessary translation for re-routing the call to the nearest sub-tandem exchange. The combinations in which relays are operated are shown by the following table Terminal Sub tandem Relays operated over which exchange ove:I wiper 1p operation is eeeted 1 STA ST1 2 STB ST2 3 STC ST3 4 STA and STB ST4 from the main tandem exchangev or sub-tandem exchange is controlled over wipers 4p, 5p and 6p.

What we claim as new and desire to secure by Letters Patent is 1. In a telephone system employing register controllers to direct the setting up of connections over serially related trunk grou s, means effective depending upon an all-trun sbusy condition being encountered at a trunk group during the setting up of a connection to transmit a characteristic signal back over the trunk conductors of the partially set up connection, and means in the re ster controller responsive to said signa to cause the release of the partially set up connection and to control the transmission of trains of impulses having a value different from the value of the trains of impulses normally transmitted, to set the desired connection up over another route.

2. n a multi-exchange telephone system having a tandem exchange provided with trunk lines to each of a plurality of the remaining exchanges in the system, register controllers arranged to transmit trains of impulses to effect the setting up of desired connections, trunk lines interconnecting certain of the exchanges of the system directly and independent of said tandem exchange, means effective depending upon an attempt to set up a connection from a calling exchange to a called exchange over a direct trunk extending between the two exchanges proving unsuccessful for transmitting a characteristic signal back over the partially set up connection to the register controller, and means in the register controller responsive to said signal for causing the partially set up connection to be released and for effecting the transmission of further trains of impulses of a.

lli

value such as to eiect the setting up of the desired connection by way of the tandem exchange.

3. In a multi-exchange tele hone system wherein trunk lines extend irectly from a first exchange to leach of a plurality of other exchanges, a plurality of tandem exchanges, trunk lines extending from said first exchange to each of said tandem exchanges, other trunk lines extending from the tandem exchanges, to said other exchanges, whereby connections may be set up from said first exchange to said other exchanges either by way of the direct trunk lines or by way of an appropriate one of said tandem exchanges, register, controllers in said iirst exchange arranged to transmit trains of impulses or controlling the setting up of connections, means effective depending upon an attempt to set up a connection over direct trunks extending between said first exchange and any one of said other exchanges proving unsuccessful to transmit a characteristic signal back to the register controller, and means in said register controller responsive to said characteristic signal for causing the release of the partially set up connection and for causing additional trains of impulses to be transmitted to effect the extension of the connection by way of theappropriate one of said tandem exchanges.

4. In a multi-exchange telephone system employing register controllers arranged to transmit series of routing digits in response to the dialling of exchange designations, respectively, means for transmitting a distinctive signal to a register controller after it has sent out one or more routing digits of a series, and means in the register controller responsive to said distinctive signal for sending out a series of routing digits common to a plurality of the exchanges of the system, and for then sending out a series of routing digits specific to the instant wanted exchange.

5. In a register controller for use in a multi-exchange telephone system in which the setting of automatic switches is effected by the transmission of successive trains of impulses, a register switch arranged to be set in response to incoming impulses characteristic of any one of a plurality of exchanges, a multi-position control switch and means for advancing said switch through its successivepositions as trains of impulses are retransmitted, circuit connections whereby said control switch in its initial positions connects up certain Wipers in turn of the register switch to control the transmission of impulses corresponding to the wanted exchange in accordance with which the register switch is set, other circuit connections whereby said control switch in later positions controls the transmission of one or more trains of impulses which are the same for a plurality of wanted exchanges, and still other circuit connections whereby said control switch in further positions thereof connects up additional wipers of the register'switch to control the transmission of -further trains of impulses specific to the instant .wanted exchange.

6. Ina telephone system wherein connections are extended from calling lines to called lines by way of serially related groups of trunk lines, automatic switches associated with said trunk lines and operable to interconnect them as desired for the purpose of extending telephone connections, reglster controllers arranged to respond to the control exercised over calling subscribers lines to eiect a correspondin routing of the calls to desired lines, there eing a plurality of routes Aover which connections can be set up, means eli'ective responsive to an attempt to operate automatic switches to set up a desired connection by way of a route when all the trunks constituting such route are in use for making an application of booster battery to the third conductor of the partially established connection, and means in the register controller responsive to said application of booster battery for effecting the rerouting of the call over an alternative route.

7. In a telephone system wherein automatic switches are controlled from register senders to set up telephone connections over alternative trunk lroutes, means effective when an attempt made to set up a connection over one trunk route proves unsuccessful to apply low-frequency alternating current to the speaking leads of the partially set up connection, a polarized relay responsive to said alternating current, and means in the register controller controlled by said polarized relay to effect a rerouting of the call.

8. In a register controller for use in a telephone system in setting up connections over alternative trunk groups, said `register controller being arranged to respond to control received over a connection partially established over one trunk route to reroute the call over another trunk route, a lead extending to said register controller over which the release of the register controller is arranged to be forced under predetermined conditions, and means for exercising the rerouting control over said director by way of said lead.

9. In a register controller for use in a telephone system to direct the setting up of connections through alternative trunk groups, said register controller having a holding and guarding lead extended thereto, means in said register controller arranged to respond to a control exercised from a trunk line over which an attempt is being made to set up a connection by way of a given route, when all the trunks line forming such route are in use, for causing the call to be rerouted, and means for edecting said control over said holding and guarding lead extending to the register controller.

10. In atelephone system employing register controllers to control the settin up of connections by way of automatic switc es and through interconnecting trunk lines, trunk groups associated with certain levels of an automatic switch, each `of said trunk groups forming one of two alternative paths over which connections may be set up to a lven destination, normal-post springs on sai automatic switch arranged to be actuated when the switch is brought into /association with one of said certain levels, means controlled through said normal-post springs Whenever all the selected trunks in the level are found to be busy for exercising a characteristic control over the register controller, and means in the register controller responsive thereto for effecting the rerouting of the call over an alternative trunk route.

11. A telephone system as claimed in claim 4, in which said second series of routing digits characteristic of the desired exchange is different from the first series of routing digits characteristic of the desired exchange.

12. A register controller as claimed in claim 5, in which the trains of impulses which are the same for a plurality of exchanges are those necessary to cause the connection to be set up to a tandem exchange.

13. In a register controlled as claimed in claim 5, in which said trains of impulses which are the same for a plurality of exchanges are those required to cause the connection to be set up to a tandem exchange, means automatically eli'ective in the event that the exchange to which a connection is being set up is one normally reached by way of the tandem exchange for causing the control switch to advance to the position corresponding to the last mentioned trains of impulses before any impulses are sent out.

14. In a register controller as claimed in claim 5, in which said control switch has a plurality of wipers, a changeover relay arranged to be energized due to the transmission back of an all-trunks-busy signal to secure the automatic advance of the wipers of the control switch through the initial positions, and means controlled through a plurality of the wipers of said control vswitch for securinn the local operation of said relay when t e called exchange is one normally reached through the tandem exchange and for causing the preliminary advance of said control switch to its initial position before any impulses are retransmitted.

15. In a register controller as claimed in claim 5, a relay in said register controller v arranged to be energized responsive to the transmission back'of an all-trunks-busy signal, and means controlled by said relay for causin the automatic advance of said control swltch through the second set of positions in the event the relay is not energized and for causing the second group of trains of impulses to be transmitted in the second group of positions inthe event that the relay is energized. 16. In a register controller as claimed in claim 5, for use in a system including a plurality of tandem exchanges, to one of which the trains of impulses transmitted in the second group of positions of the control switch are arranged to direct the call, a set of relays operable switch to select a value for the last-mentioned trains of impulses depending upon for which tandem exchange the register has been set. -In testimony whereof I have signed at London, England this 8th day of May 1931.

CHARLES GILLINGS.

y way of a wiper of said registerl In testimony whereof I have signed at FRANCIS TATLOCK BE AS. 

